I tried to edit a product from cart by clicking the native 'edit' button.
Then Magento redirected me to the page : checkout-cart-configure catalog-product-view product-id
Here, I've noticed that it's impossible to save the new product configuration in the cart, if the quantity is not change, as long as the quantity already added in cart is greater than half of the stock
For example, Do the test with a simple product with custom options that is in stock (quantity of 10). In case you don't agreebackorders (admin panel / configuration / inventory / product stock options)
If your customer add a quantity of 6 of this product in cart and then click on the 'edit' button in cart page,
Here, if customer choose or change product's options, and keep the same quantity (6) and click 'update cart' button,
Then Magento return error message (the quantity is not available).
So it seems that behind this update button, Magento add the new selection to the cart before delete the previous one..
Any fix for this would be appreciate